Testing apparatus and method of testing



June 29, 1937. R. E. sTURM Er Al.

TESTING APPARATUS AND METHOD OF TESTING Filed Dec. 16, 1935 2Sheets-Sheet l INVENTORl .lune 29, 1937.

R. E. STURM El' AL TESTING APPARATUS AND METHOD OF TESTING Filed Deo.16, 1935 2 Sheets-Sheet 2 73 3\ foo CONTINU/TY L vrToRNimCdJ Patented.lune 29, 1937 UNITED STATES PATENT OFFICE TESTING APPARATUS AND METHODF TESTING tion of Delaware Application December 16, 1935, Serial No.54,594

7 Claims.

This invention relates to testing apparatus and a method of testing, andmore particularly toapparatus and a method for testing coils,transformers and the like, such as those used in ignition systems forinternal combustion engines.

An object of this invention is to provide apparatus and a method oftesting coils, such as those used in ignition circuits, which effect a10 dependable determination of the value or condition of the coiltested.

Another object of this invention is to provide apparatus and a method oftesting ignition coils and the like, which apparatus and method indilcate the presence of short circuited turns, leaky insulation, excessiveiron loss, internal breakdown, etc., as Well as an open circuit in thecoil.

Another object of this invention is to provide a method and apparatus oftesting ignition coils and the like that provide for a predeterminedheating of the coil and for testing under heated conditions as a part ofthe complete test of the coil.

Another object of this invention is to provide apparatus for the testingof coils, which apparatus can be adjusted at the time of the test togive accurate determinations under the conditions of the test.

Another object of this invention is to provide a complete coil testingapparatus that will clearly indicate even small defects in coils, andthat can be embodied into a compact unit.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings, wherein a preferred embodi- I ment of the present invention isclearly shown.

In the disclosed embodiment of this invention, the above stated objectsare accomplished by a method of testing which comprehends the steps ofintermittently applying a direct current to the coil being tested sothat magnetic flux is intermittently built up around the turns of thecoil, and obtaining an indication of the condition of 7 the coil bymeasuring an electrical quantity that is dependent upon the rate ofdamping of flux oscillations through the turns of the coil when nodirect current is being applied to the coil.

The method also preferably includes the steps of making suchmeasurements before and after heating the coil.

Also in the disclosed embodiment, the apparatus for accomplishing theseobjects comprehends a source of direct current, the coil to be tested, acircuit interrupter for periodically con- (Cl. F-183) predeterminedamount. It is also preferable, as 10 disclosed, to provide means foradjusting the apparatus at the time of making the tests.

In the drawings:

Fig. l is a schematic circuit diagram embodyl5 ing the present inventionin a preferred form. Fig. 2 is a perspective view of a unitary structureembodying a preferred form of the present invention.

Figs. 3, 4, and 5 are schematic circuit diagrams of separated portionsof the circuit shown in 20 Fig. 1.

With particular reference to Fig. 1, a source of direct current, such asa battery I 0, preferably has a potential suitable for the proper normaloperation of a coil or electrical transforming device that is to betested. One side of the battery Ill is connected to a movable contactcarrying arm I2 of a switch I4, which contact carrying arm has contactsI8 and I8 mounted on opposite sides thereof. The contact carrying arm I2is preferably resilient, and biases the contact I6 into engagement witha stationary contact 2B that is mounted on a contact carrying arm 22.'I'he contact carrying arm 22 is connected to a terminal or binding post24. The switch I4 is provided with a manually operable operating member26 having a cam 28 mounted thereon that engages the contact carrying armI2 to effect movement of that contact carrying arm and control of thecontacts that are mounted thereon. When the contact carrying member I 2is moved by the operating member 2B and cam 28 against the normalbiasing force thereof, the contacts I6 and 20 are opened, and thecontact 4- I8 engages a stationary contact 30 that is mounted on acontact carrying arm 32. The contact carrying arm 32 is connected to thecommon ends of a secondary winding 34 and a primary winding 36 of astandard coil 38. 'Ihe standard 50 coil 38 has a core 40 through whichthe primary and secondary windings thereof are magnetically coupled.Stop members 42 that cooperate with a projecting portion 44 on the cam28 are provided for limiting the movement of the operating 55 member 26.The other side of the battery l is connected through breaker points 45and d8, a breaker arm 50 and a spring 52 of a circuit breaker 55 to theother end of the primary winding 36 and to a terminal or binding post54.

The contact d5 is .preferably a stationary contact, and cooperates withthe movable Vcontact 48 that is Amounted near the end of the breaker arm50,'which breaker arm is pivotally mounted at 55. The spring 52 biasesthe breaker arm 50 toward the contact L35. A-bumper block 58 is securedto the breaker arm intermediate vthe ends thereof and cooperates with arotatable cam 50, which cam, when rotated, intermittently andperiodically moves the breaker arm against the force of the spring 52-toeiect periodic breaking of the contacts @l and d8. Hence, when thebreaker is operated, an intermittent or periodically interruptedpotential is normally applied to the terminals cr binding posts 24 and54; or when-the cont-acts I5 and 30 are engaged, to Vthe primarywinding( 3G of the standard coil 38. lThe secondary winding 3d of thestandard coil Siiis preferably opencircuited;

.. The .breaker arm50,-contacts l5 and 68, spring.

52 and cam 50 are preferably mounted in a housingr as indicated at 52.The cam 50 is preferably mountedona sl'iaft 513 that is drivinglyconnected to .adrivingniotor 55, which motor is preferably.l iasubstantially constant speed alternating currentniotorhaving a fieldVwinding 63 and a rotor l0..,fle1niinals l2 and 'Hi are connected to analternating .current power supply line indicated by the leads and lil.vOne end of the eldtwinding 8 is connected to `the terminal` l2, andtheother end of the field Winding 58 is connected .throughaswitch 80tothe terminal 1li, so that the switchfu-controls rthe operation of themotor 66.

A .condenser 82 isv connected'V across the -contact's and l to limit andreduce sparking at those contacts. One end of a primary winding 84 of a.transformer .85 is connected to the 'contact l5. The other end of theprimary winding llis connected through .a resistor 88, the spring 52 andbreaker Varm-50 to the contact 48. Thus, the 'condenser- 82 alsoprovides a lump capacity inthe primary circuit of the coil that isconnected thereto, which condenser and primary Winding forman-oscillatory. circuit. The transformer ..85 has ra secondary winding l90 that is connected V,across `the terminals 92 of a meter or indicatingv.device 9d. VThe transformer 80 also has acore .96 throughwhich Vthewindings Sli and 50.are. magnetically coupled. f The coreii ispreferably movable, as b-y sliding for varying the magnetic .couplingbetween the windings 84 and 55.', A.manuallymovableactuating member 98issecured to the .core .96v for adjusting the transformer coupling. .3 I

.'Ilo,` provide a continuity test circuit, the terminal .l2'is.connectedto a terminal orbinding`post l00';.,and theterminal lil is connected toa.l terminal or binding post |02 through an indicatingdevice lllthat ispreferably a gaseous d''tcharge tube having electrodes Illia` sealedinto a glass container E08. A

Since it ,is desirable to test some coils `when they .are heated, aswellas .when they are cold, it `is .desirable to provide .a circuit forelectricallyv .heating the coil to be tested by a predetermined amount.A circuit is therefore provided forso heating, the coil Vto be tested.rllhat is, the primary winding M0 of a transformer H2 is connecteddirectly totheterminal 16, and to the terminal 'l2 through a switch H4,which switch is provided with means H5 for opening the switch after ithas been closed for a predetermined time interval. The transformer ||2has a core Il@ and a secondary winding that is magnetically coupled tothe primary Winding I l0 through the core H8. The secondary winding |20is connected to terminals or binding posts |22 and |2li. The switch llllhas a contact carrying arm |25,vupon which is mounted a contact |28in alignment for engagement with a cooperating stationary contact |30.The contact carrying arm is moved to effect engagement of the contacts|23"and E55 by movement of a manually operable member |32. That is, thecontact carrying arm E25 has projecting ngers |365 and B thereon thatare in alignment for engagement with a cam ISE thatis mounted on, androtatable with a shaft |40. Whether the cam E38 engages the finger |135or the finger |36 depends upon the direction of movement of the cam |38.lThe shaft Vis connected-to vthe manually operable member v|32 through aspring escapement mechanism indicated diagrammatically at |42'. lIlheYclosing of thecontacts |28 and |35 by operating the manually operablemember .|32 winds up a spring in the escapement mechanism,the recoil ofwhich spring is time controlled and `effects disengagementY of thecontacts E28 and |30. f-

A panel on which themanually operable control members 25, 90, and |32are mounted; is indicatedv at M4. I

With particular reference to Fig. 2, a unitary structure is there shownwhich Vembodies the circuit and apparatus disclosed in Fig. '1; andreference 4numerals similar to'those previously used in describing thestructure-and circuitvof Fig. 1 referto similar partsfin- Fig. 2. Inthis unitary structure, a housing |50 preferably encloses the apparatus,except for-the direct current supply or battery l0-which Vis placedoutside of the housing and connected to suitable binding posts, notshown. The panel Idd-comprises a part of Athe housing |50. On this panelMld the terminals or binding .post 24 and 54, y|00 and |02, and |22 and|24, which are preferably jack type terminals into which connectingwires or plugs may be inserted, 'are-insulatingly. mounted on insulatingblocks |52, l54 and i5jrespecthe control knobs are indicator plates |64,v|00 and |58 respectively which designate the purpose andpositions ofthe knobs. Theiindicating devices 9d' and Ill/inthe switch 30 `and thecircuit breaker are `preferably-mountedon a separate vpanel '-lflilioithe housing |50. Y The housing of ther-indicating device S4 4and lthehousing 62 lof the circuit lbreaker 55 are preferably provided lwith-fianges il; and VMk respectively, which are secured to the panel |10byiscrews |16, or other suitable fastening means. f

In Figs. 3, 4, and 5, parts `of the circuitshown in Fig. l that yareutilized for making different tests on a coil yare separated -tofclarifyand simplify the explanations thereof. In these figures also, referencenumerals similar -to those Vpreviously used refer to similar parts.A V-t In vthe-operation of the dev-ice, the testing of a coil ortransforming ydevice includes `several steps. That is, (l) the testingof the coil foricontinuityof the windings either before,` or after thecoil is heated, or both; (2) the testing of the coil for grounds, shortcircuited turns and other losses either before or after heating, orboth;

and (3) the heating of the coil.

Continuity test-The circuit for testing the continuity of a coil windingis included in the circuit shown in Fig. 1, but is separately shown inFig. 3. In making this continuity test, preferably alternating currentis supplied to the terminals I2 and 14. The coil, the continuity ofwhich is to be tested, is connected across the terminals IIlEI and I 62.IfV the coil is continuous, and has no breaks in the winding, theindicating device or gaseous discharge tube |04 will provide anindication due to the current flow therethrough.

Test fmshort circuited turns and other tosses- The circuitfor testing acoil for short 'circuited turns is included in that shown in Fig.

l, and is separately shown in Fig. 4. In making the test for shortcircuited turns, the circuit breaker is started by closing the switchwhich closes the circuit to the circuit breaker driving motor 66. rIheswitch I4 is then operated to effecty engagement ofthe contacts I8 and3U to close the circuit to the primary winding 36 of the standard coil38. Each time the contacts 46 and 46 of the circuit breaker are closed,the primary winding 36 is energized from the battery Ill through thosecircuit breaker contacts. This energization of the primary winding 36builds up a flux in and around the primary winding 36, core 49 andsecondary winding 34. 'I'he closing of the circuit breaker contacts 46and 48 also short circuits the primary Winding 84 of the transformer86through the resistor 88. However, when the circuit breaker contacts 46and 48 break, the flux in the standard coil 38 collapses, and incollapsing, creates a potential across the winding 36 and condenser 82which potential controls the current flow through the primary winding 84of the transformer 86 While the circuit breaker contacts are open. Theaverage Value or magnitude of the potential across the primary winding36 is necessarily dependent upon the rate of dam-ping of the flux oroscillations through that winding. The fact that the condenser isconnected across the winding makes the circuit oscillatory. 'Iheoscillatory current in the oscillatory circuit consequently effects anindication on the indicating device 94, the value of which indication iscontrolled by setting the core 96 of the transformer 86 and therebyregu-lating the magnetic coupling between the windings 84 and 9i) ofthat transformer. The core 96 is preferably so set that a predeterminedindicated value, such as at the line marked set on the indicator dialshown in Fig. 2, is indicated by the indicating device 94.

After this setting operation, and without changing the setting of thecore 96, the speed of the motor 66 or the potential of the battery I0,the switch I4 is operated to eect engagement of the contacts I6 and 20.The primary Winding of the coil to be tested being now connected acrossthe terminals 24 and 54, that coil is connected into the circuit. Thesecondary winding of the coil of the transforming device to be tested ispreferably left open. Since the value of the indication provided by theindicating device 94 is dependent upon the alternating or oscillatingcurrent in the oscillatory circuit and the rate of damping of thatcurrent, the indicating device 94 will provide an indication dependentupon the coil to be tested, because the losses in the coil directlyeffect rate of damping of the current oscillations. Also, since shortcircuited turns in either of the magnetically coupled primary orsecondary windings or other losses in the coil to be tested tend tocause quicker damping of the oscillations in the coil, the indicationprovided by the indicating device 94 will be decreased to a value belowthe normal or proper value for the coil by such short circuited turns,because of the decrease of the average current effected by the morerapid damping. Knowing the proper or normal indicated value for a coilor transforming device having certain characteristics, this circuit andapparatus consequently provides a definite indication as to whetherthere are any short circuited turns in either winding, or, in otherwords, whether there are any abnormal electrical losses in the coil, ortransforming device.

Heater circuit-In order to determine Whether the performancecharacteristic of a coil or transforming device are satisfactory whenthe coil is heated, as Well as when it is cold, it is desirable to testthe coil after it has been heated. The most convenient Way to heat thecoil internally is to apply a current, and preferably an alternato ingcurrent thereto. However, to insure the heating of the coil by apredetermined amount and to prevent excessive heating, the currentshould be applied thereto for only a predetermined time interval. In thepresent system, the coil or trans- 51T forming device to be heated isconnected across the terminals I22 and |24. The circuit thereto is thenclosed through the transformer H2 by operating the time control switch II4 which automatically opens the circuit after a predetermined timeinterval. The transformer H2 is provided to limit or control the voltagethat is applied to the Winding of the coil.

From the foregoing description of the construction and mode of operationof the present apparatus for testing electrical coils, it will beclearly understood that the apparatus includes a source of directcurrent I Il, a coil I I2 to be tested, a circuit interrupter 55 forperiodically connecting the said coil I I2 to the direct current sourceI0, means 82 connected to the coil II2 for effecting a dampedoscillatory decay of the flux of the coil during interruptions of thecircuit interrupter 55, and means 94 connected to the direct currentcircuit to the coil II2 for measuring an electrical quantity dependentupon the rate of damping of flux oscillations in the coil II2.

W'hile the embodiment of the present invention as herein disclosed,constitutes a preferred form, it is to be understood that other formsmight be adopted, all coming within the scope of the claims whichfollow.

What is claimed is as follows:

1. The method of testing a coil, comprising the steps of intermittentlyapplying a direct current to the coil so that flux is intermittentlybuilt up around the turns of the coil, and obtaining an indication ofthe condition of the coil by measuring an electrical quantity that isdependent upon the rate of damping of flux oscillations through theturns of the coil when no direct current is being applied to the coil.

2. The method of testing a coil, comprising the steps of intermittentlyapplying a direct current to a standard coil at a substantially constantrate so that flux is intermittently built up around the turns of thestandard coil, quantitatively measuring a Value dependent upon the rateof damping of an oscillatory current in the standard coil, substitutingthe coil to be tested for the stand- CIL ard coil so that the directcurrent is intermittently applied thereto at substantially the samerate, and quantitatively measuring an electrical value dependent uponthe rate of dampingof an oscillatory current in the coil being tested. Y

3. The method of testing a coil, comprising the steps of intermittentlyapplying a direct current of constant potential to the coil at asubstantially constant rate so that flux is intermittently built uparound the turns of the coil, measuring an electrical quantity that isdependent upon the rate of decrease in amplitude of flux oscillations othe coil, heating the coil by applying an alternating current thereto,and again intermittently applying the direct current thereto while thecoil is heated and making 3, measurement similar to that previouslymade.

4. In apparatus for testing electrical coils, the combinationcomprehending a source of direct current, a coil to be tested, a circuitinterrupter for periodically connecting thesaid coil to the directcurrent source, means connected to the coil for eiecting a dampedoscillatory decay of the flux of the coil during interruptions of the.circuit interrupter, and means connected to the direct current circuitto the coil for measuring an electrical quantity dependent upon the rateof damping of flux oscillations in the coil.

5. In apparatus for testing electrical coils, the combinationcomprehending a coil to be tested, means for heating the coil apredetermined amount, a source of direct, current, a circuit interrupterfor periodically connecting the coil to the direct current source, meanseiecting an oscillatory collapse of the flux in the coil when thecircuit interruptor is open, and means connected to the coil formeasuring an electrical quantity dependent upon the average value of theoscillatory current of thecoil during the circuit interruptions effectedby the circuit interrupter. Y

c 6. In' apparatus yfor testing electrical coils, the combinationcomprehending a coil to be tested, a source of current providingV atesting potential, a standard coil, indicating means, means including atransformer selectively connecting the indicating means to the standardcoil and the coil to be' tested, said transformer having an adjustablecore for settinggthe indication of the indicating means to apredetermined indicated value when `said indicatingmeans is connectedtothe standard coil, said indicating means then providing a quantitativeindication of the condition of the coil to be tested when connectedthereto.

7. In apparatus for testing electrical trans-'- forming devices havingprimary andsecondary device, and an indicatingdevice electricallyconnected to the transforming device and adapted to`provide a.quantitative indication, said indicating device .being so connected thatelectrical losses in the transforming device decrease the quantitativeindication of the indicating device,

RALPH E. STURM. HERMAN L. HARTZELL.

